Gen. Salem Ali Qatan, the commander of Yemen’s southern military district, was assassinated early Monday morning, underscoring the continued threat of militants despite the army’s recent gains against al Qaida-linked fighters in the country’s restive south.

According to Yemeni state media, Qatan’s convoy was traveling through the southern port of Aden on the way to his office when a Somali man wearing a suicide belt threw himself onto the general’s vehicle. Qatan, his driver and a guard were killed, and five bystanders were wounded.

The assassination came days after what military officials have characterized as a breakthrough in the fight against militants based in southern provinces of Abyan and Shabwa, where Yemeni troops – backed by local tribesmen and American air and intelligence support – managed to push al Qaida-linked fighters out of territory they’d held for more than a year.

The al Qaida militants are mostly Yemenis, according to area civilians and military officers, but a number of Somalis have fought on the side of the militant umbrella group known as Ansar al Shariah. Yemen, an impoverished nation at the southern tip of the Arabian Peninsula, also is home to tens of thousands of refugees who’ve fled across the Gulf of Aden to escape war and starvation in Somalia.

Yemen’s new president, Abed Rabbo Mansour Hadi, had appointed Qatan, a lifelong military man from Shabwa, to his position in March. Qatan replaced Gen. Mahdi Maqwala, a controversial ally of former President Ali Abdullah Saleh who’d previously led what even Yemeni military officials characterized as a halfhearted effort against the militants since they seized control of much of Abyan last spring.

Qatan's tenure initially was marred by a surprise attack on a military base that left nearly 100 soldiers dead. He’d since been hailed as a key force behind the renewed offensive in the south.

The fighters of Ansar al Shariah – formally commanded by Nasir al Wuhayshi, the head of the Yemen-based group al Qaida in the Arabian Peninsula – largely have abandoned former strongholds in Abyan since the government offensive. According to locals, al Qaida fighters also have begun retreating from Azzan, a longtime bastion in neighboring Shabwa.

While the militants’ withdrawal may be a tacit admission of weakness in the wake of the government’s unprecedented air and land assault, few Yemenis interpret it as an admission of defeat. Locals and military officials alike cautioned that the bulk of the fighters in Abyan were able to leave unimpeded and, for the most part, still armed. Some civilians in Shabwa said retreating militants had painted their withdrawal as a tactical decision to avoid concentrating fighters in one place, thus depriving the Yemeni military or American drones of obvious targets.

Some observers expect the militants, said to be fleeing mostly to the north from their former strongholds near Yemen’s southern coast, to seek refuge in more isolated areas. The central government’s control over the country has always been fragile, but it grew even weaker over the course of the uprising that began last year as part of the “Arab Spring” revolts and eventually ended Saleh’s three-decade rule.

While Hadi has made some efforts toward reorganizing the military, much of the armed forces remain split into acrimonious factions, and many areas of the country are out of the government’s hands. Security has deteriorated even in many of the larger cities, including Aden, where security officials have described an increased presence of armed gangs.

Despite the progress in Abyan, analysts and politicians cautioned, the battle against al Qaida in Yemen is far from over. In the absence of strong governing institutions, they noted, Yemeni militants probably would continue to find sufficient space to operate.

“This isn’t a problem that can be solved through the use of force,” said one tribal leader from al Jawf, an impoverished rural province on the border with Saudi Arabia, who spoke only on the condition of anonymity because of the sensitivity of the topic. “As long as the Yemeni state remains weak, al Qaida will continue to exist.”